Even with the conservative treatment, the humeral shaft fractures can be easily united with about 95% of union rate. According to Boyd(1961, 1965), the humeral shaft is the third of all the non-union of the shaft of long bones in the order of femur and tibia. From June 1978 to May 1985, 14 cases of non-union of humeral shaft were treated at Dept. of Orthopedic Surgery, Ewha University Hospital and the following results were obtained. 1) Of 14 cases, 8 were traffic accident and 4 were industrial injury. All were 20-40 age group and 13 cases were male. 2) The site was 9 cases of mid. 1/3, 3 cases of lower 1/3 and 2 of upper 1/3. The comminuted fracture was 12 cases and 2 cases were transverse. 3) The initial treatment after injury was 13 cases of operative methods; 9 cases were plate fixation; 3 cases, screw fixation; 1 case, intramedullary nailing. The other 1 case was conservative method. 4) The probable causes of non-union were complex. The most frequent one was inadequate internal fixation of 9 cases, 3 cases of inappropriate external immobilization and the other 2 were unknown. 5) 8 cases were treated with plate fixation, 2 cases with autogenous bone graft, 1 with EST(electric stimulation therapy) and 1 with intramedullary nailing. 6) Postoperative immobilization was done with long arm cast or shoulder spica cast. 7) All cases were united and the average union time was 9.1 weeks. Limitation of motion of shoulder and elbow was recovered with physiotherapy.